This application is to obtain funding for the purchase of a high resolution in vivo micro-computed tomography (microCT) imaging system for use with rodent models at the University of Connecticut Health Center. This instrument, the Scanco VivaCT40, will become part of an active MicroCT Facility. The core facility provides services to investigators from several departments within the Schools of Medicine and Dental Medicine, with a primary research emphasis in bone biology and combined annual NIH funding of $6.5 million. The facility also provides core services to investigators from Yale University and the University of Pennsylvania. Although our present microCT imaging capability has proven to be beneficial to a large number of investigators, it is limited to analysis of excised tissue samples, precluding longitudinal studies and requiring large numbers of animals for analysis at multiple time points. In vivo microCT imaging and analysis will be helpful in studies involving transgenic mouse models, allowing phenotypic quantitation of skeletal elements during maturation and aging. Likewise, current studies involving contrast-enhanced imaging of organs, tumors, and vascular structures will benefit greatly with the capability of high-resolution in vivo CT imaging and real-time perfusion of contrast media. Because ex vivo microCT imaging and morphometric analysis of excised tissue structures is nondestructive and rapid, our existing system will continue to provide essential data from specimens harvested for histomorphometric examination, gene expression assays, and mechanical integrity tests. Moreover, because the resolution of the in vivo and ex vivo systems are equivalent and analysis software identical, the Alphastations used to operate the instruments can be clustered together. The resulting increase in computational capacity will allow us to scan at the highest resolution available. Relevance to public health: The investigators who will use this instrument have developed murine models that are highly relevant to our understanding of the mechanisms of bone loss with aging, estrogen deficiency, and immobilization. The increase in the quality and quantity of results that will be obtained with an in vivo microCT system will make it possible to develop new approaches to the maintenance of bone health and treatment of bone disease more rapidly. This has been recognized as a critical issue by the Surgeon General's Report on "Bone Health and Osteoporosis". [unreadable] [unreadable]